I went to http://firefox.com/m in my N900 and it asked me if I wanted to install a mozilla repository, which would be just fine by me. But it says "Distribution: chinook" not Fremantle for some reason.

Note well! The installation procedure uses space on the main root partition (NAND). It frees it back up, but beware...

Then, after the whole thing downloaded I got:
"Memoria insuficiente en ubicación de destino"

Translated: not enough space sucker! Oh, the woes of the stupid /opt thing.

Anyway, it appears it is not optified

To free up my space again, I had to run:
Fennec never got installed. It installed xulrunner to /usr/local (I *think* it was this that installed xulrunner).

Have fun.